Physical techniques, especially calorimetry to study thermal effects and dilatometry to study volume effects, are being used together with more conventional biochemical approaches to gain insight into several important problems of biological membranes and lipoproteins. These include a) Exceedingly precise measurements of coefficients of expansion to better characterize thermal transitions in membranes and relate them to biological properties. b) Dilatometric investigations of transitions in serum lipoproteins to better understand the state of phospholipids and cholesteryl esters in them. c) Investigations of the mechanism of anaesthesia by direct dilatometric measurements of volume changes. d) Elucidation of the mechanism for control of fatty acid composition of biomembranes, and in particular the mechanism for control of membrane transition temperatures.